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Nonaqueous-electrolyte batteries and nonaqueous electrolytic solutions

a technology of electrolytic solutions and nonaqueous electrolysis, which is applied in the direction of positive electrodes, cell components, electrochemical generators, etc., can solve the problems of reducing battery safety, low thermal stability, and a substance in a charged state, and achieves high initial output, high discharge capacity, and high capacity retention

Inactive Publication Date: 2012-09-27
MITSUBISHI CHEM CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

"The patent text describes a nonaqueous-electrolyte battery that has a high initial output and can maintain its performance even after a durability test. The battery uses a specific combination of a chain ether and a compound that forms a negative-electrode coating film or protects the positive electrode. The nonaqueous electrolyte solution used in the battery contains a chain ether and a cyclic carbonate. The technical effects of this invention include improved durability, high-rate discharge capacity, and stable output performance even at low temperatures."

Problems solved by technology

Lithium cobalt oxide (LiCoO2), which is used as a positive-electrode active material as shown above, has a drawback that this substance in a charged state has low thermal stability and reduces battery safety.
Furthermore, nonaqueous-electrolyte batteries employing LiFePO4 as a positive-electrode active material have had the following problem.
When these batteries are repeatedly charged and discharged in a high-temperature environment of, for example, about 60° C., elements including iron which are contained in the active material partly dissolve away with repetitions of charge / discharge, and the dissolved iron adversely affects the negative-electrode active material constituted of a carbon material, etc.
As a result, the negative electrode itself is impaired in charge / discharge reversibility and other properties and is hence reduced in reactivity, and this tends to result in a decrease in the capacity or output of the nonaqueous-electrolyte batteries.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

Production of Negative Electrode

[0321]To 98 parts by weight of artificial-graphite powder KS-44 (trade name; manufactured by Timcal) were added 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose (concentration of sodium carboxymethyl cellulose, 1% by mass) as a thickener and 2 parts by weight of an aqueous dispersion of a styrene / butadiene rubber (concentration of styrene / butadiene rubber, 50% by mass) as a binder. The ingredients were mixed together by means of a disperser to obtain a slurry. The slurry obtained was applied to one surface of a copper foil having a thickness of 10 μm and dried. This coated foil was rolled with a pressing machine to a thickness of 75 μm, and a piece of a shape having an active-material layer size with a width of 30 mm and a length of 40 mm and having an uncoated area with a width of 5 mm and a length of 9 mm was cut out of the rolled sheet. Thus, a negative electrode was obtained.

[Production of Positive Electrode]

[0322]Nin...

example 2

[0331]A sheet-form lithium secondary battery was produced and evaluated in the same manners as in Example 1, except that an electrolytic solution was obtained in a dry argon atmosphere by mixing 99.5% by mass mixture of ethylene carbonate (EC), dimethoxyethane (DME), and ethyl methyl carbonate (EMC) (volume ratio, 2:3:5) with 0.5% by mass vinylene carbonate (VC) and then dissolving sufficiently dried LiPF6 in the resultant mixture so as to result in a proportion thereof of 1.1 mol / L. The components of the electrolytic solution and the results of the evaluation are shown in Table 1 to Table 3.

example 3

[0332]A sheet-form lithium secondary battery was produced and evaluated in the same manners as in Example 1, except that an electrolytic solution was obtained in a dry argon atmosphere by mixing 99.5% by mass mixture of ethylene carbonate (EC), dimethoxyethane (DME), and ethyl methyl carbonate (EMC) (volume ratio, 2:3:5) with 0.5% by mass lithium difluorophosphate (LiPO2F2) and then dissolving sufficiently dried LiPF6 in the resultant mixture so as to result in a proportion thereof of 1.1 mol / L. The components of the electrolytic solution and the results of the evaluation are shown in Table 1 to Table 3.

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Abstract

The invention is to provide a nonaqueous-electrolyte battery which comprises a current collector, a positive electrode containing a lithium-containing phosphoric acid compound represented by LixMPO4 as a positive-electrode active material, a negative electrode containing a negative-electrode active material capable of occluding and releasing lithium ions, and a nonaqueous electrolytic solution containing a chain ether and a cyclic carbonate having an unsaturated bond.

Description

TECHNICAL FIELD[0001]The present invention relates to nonaqueous-electrolyte batteries. More particularly, the invention relates to nonaqueous-electrolyte batteries which employ nonaqueous electrolytic solutions that bring about excellent high-output characteristics and excellent durability when iron lithium phosphate is used as the positive electrode.BACKGROUND ART[0002]Nonaqueous-electrolyte batteries including lithium secondary batteries are being put to practical use in extensive applications ranging from power sources for appliances for so-called public use, such as portable telephones and notebook type personal computers, to vehicle-mounted power sources for driving motor vehicles or the like. However, nonaqueous-electrolyte batteries are increasingly required to have higher performance in recent years, and are required to attain battery characteristics, such as, for example, high capacity, high output, high-temperature storability, cycle characteristics, and high safety, on a...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01M10/0564H01M10/056H01M10/0525H01M10/0567H01M10/0568H01M10/0569
CPCH01M4/5825H01M10/0525H01M10/0569Y02E60/122H01M10/0564H01M2300/0037H01M10/0568H01M4/587H01M10/0567Y02E60/10H01M4/58H01M10/052H01M2004/028H01M2004/027
Inventor TOKUDA, HIROYUKI
Owner MITSUBISHI CHEM CORP
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